Reflection type color liquid crystal device and method for driving the same using a color filter

ABSTRACT

Reflection type color liquid crystal device, which can display bright and clear colors, is provided. Further, this reflection type liquid crystal device is configured so that a first substrate provided with a transparent electrode, and a second substrate provided with a transparent electrode and a color filter are placed in such a manner as to face each other. Moreover, a pair of polarizing plates are placed at both sides of the substrates thereacross. Furthermore, a reflector plate is provided outside of one of the pair of the polarizing plates. The color filter is composed of filter elements respectively corresponding to the subtractive primaries, namely, yellow, cyan and magenta.

FIELD OF THE INVENTION

The present invention relates to a reflection type liquid crystaldisplay device, and to a method for driving a reflection type colorliquid crystal device.

BACKGROUND TECHNOLOGY

A display equipped in a portable information terminal should be of thelow power consumption type. Thus, a reflection type liquid crystaldevice, which does not need back light, is most suited for such anapplication. However, the dominating conventional reflection type liquidcrystal device is of the monochromatic display type. Therefore, goodreflection type color display has not been obtained yet.

Full-scale development of the reflection type color liquid crystaldevice was started about the middle of 1980's. There had been only asuperficial understanding before then. For example, the reflection typecolor display could be obtained by replacing the backlight unit of thetransmission type color liquid crystal device.

However, when the liquid crystal device is actually made of such aconfiguration, it has been found that only very dark display could beachieved and that the device of such a configuration was not practical.There have been three causes. First, the polarizing plate has discardedmore than half of the quantity of light. Second, the color filter hasdiscarded more than ⅔ of the quantity of light. Finally, there has beenthe problem of a parallax. Parallax has been the inevitable problem inthe case of TN (twisted nematic) mode and STN (supertwisted nematic)mode. This is because of the fact that two polarizing plates arenecessarily used in these modes and thus there is a distance createdbetween the reflector plate and the liquid crystal layer, which cannotbe disregarded, unless the polarizing plates are not built in a cell.Incidentally, the problem of the parallax referred to herein is not theproblem of a double-image in the display which has occurred even in theconventional reflection type monochromatic liquid crystal device.Namely, the parallax is a problem that occurs in and is peculiar to thereflection type color liquid crystal device.

Problems of parallax will be described hereunder by referring to theaccompanying drawings. FIGS. 7(a) and 7(b) are sectional views of areflection type color liquid crystal device utilizing TN mode or STNmode. This liquid crystal device consists of an upper polarizing plate1. an upper glass substrate 2, a liquid crystal layer 3, a lower glasssubstrate 4, a lower polarizing plate 5, an optical reflector plate 6and red-green-blue (RGB) three-color filter 7. Additionally, there aretransparent electrodes, an orientation film and insulating film betweenthe upper and lower glass substrates. These composing elements are,however, unnecessary for describing the problem of a parallax. Thus, thedrawing thereof is omitted.

Meanwhile, there are two problems with the parallax. First, one of thetwo problems is color cancellation. As shown in FIG. 7(a), an observer32 watches reflection light 31 having passed through a green filter.This reflection light has been mixed with incident light 30 which hasbeen incident thereon through the red-green-blue color filter and hasbeen diffused and reflected by the reflector plate. If the thickness ofthe lower glass substrate 4 is sufficiently large in comparison with thepitch of filter elements of the color filter 7, a light ray propagatedthrough any color filter element is mixed with the reflection light 31with same probability.

However, the light of any wavelength, which has passed through the paths“red to green” and “blue to green”, is inevitably absorbed by one of thefilter elements. Thus, only the light having passed through the path“green to green” remains. This is the same with reflection light rayshaving transmitted from the blue and red filter elements. Consequently,the brightness of displayed white is decreased to ⅓ that of the case inwhich there is no parallax.

A second problem is that the displayed colors become dark. FIG. 7(b)illustrates a green displaying state. Further, the cross hatched portionof the liquid crystal layer 3 indicates that such a portion is in anon-illuminated state (namely, a dark state). Incident light 30 passesthrough each of red, green and blue dots with the same probability.However, ⅔ of the quantity of the incident light 30 are absorbed by thered and blue dots which are in an off-state. Furthermore, after diffusedby the reflector plate 6 and mixed with the reflection light, ⅔ of thequantity of such light are absorbed by the red and blue dots which areput into the off-state again. Then, the light reaches the observer 32.Therefore, the brightness of the display of green is obtained bysubtracting the quantity of light, which is absorbed by the green filterelement, from {fraction (1/9)} of the brightness of the displayed white(namely, {fraction (1/9)} of the brightness of the display of white—thequantity absorbed by the green filter element), and thus becomes verydark.

As is understood from the foregoing description, it is very difficult toapply TN mode and STN mode, in each of which the problem of the parallaxoccurs, to the reflection type color liquid crystal device.

Thus, hitherto, attempts have been made to obtain bright reflection typecolor displays by changing the liquid crystal mode.

For example, according to the article by Mr. Tatsuo Uchida et al. (IEEETransactions on Electron Devices, Vol ED-33, No. 8, pp. 1207-1211(1986)), as illustrated in FIG. 2 therein, the comparisons of thebrightness among various liquid crystal modes are made. As aconsequence, PCGH (Phase-Change type Guest Host) mode, which does notneed polarizing plates, is employed. Furthermore, in the case of theJapanese Unexamined Patent Publication No. 5-241143 Official Gazette,PDLC (Polymer-Dispersed type liquid crystal) mode, which does notrequire the polarizing plates, is employed so as to realize a reflectiontype color liquid crystal device.

In the case of using the liquid crystal mode which does not needpolarizing plates, there are obtained the merits in that the absorptionof light by the polarizing plate is eliminated and that the problem ofthe parallax can be settled completely by providing a reflector plate insuch a manner so as to be adjacent to the liquid crystal layer.

However, on the other hand, in the case of the liquid crystal modesrequiring no polarizing plates, the contrast is usually low. Further,especially, PCGH mode has encountered the problem in that halftonedisplay cannot be performed owing to the presence of a hysteresis in thevoltage-transmittance characteristic. Furthermore, these liquid crystalmodes, by which foreign substance is added to the liquid crystal, haveencountered the problem in degradation in the reliability.

Therefore, TN mode and STN mode, which have been widely used heretoforeand achieved satisfactory results, are the best modes to be employed, ifcan be used even in the aforementioned conditions.

Additionally, hitherto, attempts have been made to obtain a brightreflection type color display by using the bright color filter. Anexample of this is disclosed in the Japanese Unexamined PatentPublication NO. 5-241143 Official Gazette. In this case, a reflectiontype color liquid crystal device is configured by using a color filterconsisting of filter elements respectively corresponding to thesubtractive primaries, namely, yellow, cyan and magenta.

This method has profound effects in obtaining bright displays but hasfaced the following problems.

Namely, ordinary color liquid crystal devices perform the additivemixing process by using a set of small color points, and thus use thecolor filter consisting of filter elements respectively corresponding tothe additive primaries, namely, red, green and blue. However, accordingto the aforementioned Official Gazette, the additive mixing process isperformed by using the color filter corresponding to the subtractiveprimaries. Thus, the degree of the color saturation of the displayedcolor is low, and the clear display cannot be achieved. Incidentally,according to the same Official Gazette, PDLC mode, which does not usepolarizing plates, is employed. In addition, no parallax is caused as aresult of providing the reflection plate at a place adjacent to theliquid crystal layer across the color filter.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide areflection type liquid crystal device which can obtain a bright displayby using a color filter consisting of filter elements respectivelycorresponding to Yellow, cyan and magenta, and can display bright colorsin comparison with the conventional devices by making good use ofparallax.

In accordance with the present invention, there is provided a preferableembodiment of a reflection type color liquid crystal device, which has aliquid crystal cell, in which a liquid crystal layer is held between afirst substrate provided with a transparent electrode and a secondsubstrate provided with a transparent electrode and a color filter,wherein the liquid crystal cell is placed between a pair of polarizingplates, wherein an optical reflector plate is formed outside one of thesubstrates, and wherein the aforementioned color filter comprises filterelements respectively corresponding to subtractive primaries that areyellow, cyan and magenta color elements, and wherein the lowesttransmittance of the color filter, which correspond to each of the colorelements, is not less than 10%.

Thus, the reflection type color liquid crystal device, which realizes abright and clear display, can be obtained by setting the lowesttransmittance of the color filter, which corresponds to each of thecolor elements, as being not less than 10%. Generally, the range ofwavelengths from 400 to 770 nm is referred to as the visible region.Especially, the human visual sensitivity is high in the range ofwavelengths from 450 to 660 nm. Therefore, a bright and clear displaycan be attained by setting the transmittance of the color filtercorrespondingly to each of all of the color elements as above described.

Further, regarding the color filter, the lowest transmittance thereofcorresponding to each of the color elements in the visible region is setat a value within a range of 15% to 25%.

Further, a preferable embodiment of the reflection type color liquidcrystal device of the present invention is adapted so that the spectrumrepresenting a transmission characteristic of the aforesaid yellowfilter element intersects with the spectrum representing a transmissioncharacteristic of the aforesaid magenta filter element at a wavelengthbeing close to 500 nm, wherein the spectrum representing a transmissioncharacteristic of the aforesaid cyan filter element intersects with thespectrum representing a transmission characteristic of the aforesaidmagenta filter element at a wavelength being close to 600 nm, andwherein these two points of intersection are present in a range where atransmittance is not less than 30%. More preferably, the aforesaid colorfilter is formed so that the two points of intersection are present in arange where the transmittance is 35% to 60%.

Moreover, a preferable embodiment of the reflection type color liquidcrystal device of the present invention is adapted so that a distancebetween the optical reflector plate and the color filter is set as beinglarger than the pitches of dots formed by the aforesaid electrode. Morepreferably, the distance between the optical reflector plate and thecolor filter is set as being twice to three times each of the dotpitches. Incidentally, it is not desirable that the thickness of theglass substrate becomes larger than 0.7 mm. This is because the doubleimage of the display is conspicuous. With such a configuration, thecolor saturation of the displayed colors is enhanced by the subtractivemixing which utilizes the parallax.

Furthermore, a preferable embodiment of the reflection type color liquidcrystal device of the present invention is adapted so that a pixelelectrode is placed on one of the aforesaid substrates in such a manneras to be formed like a matrix, and that a switching element is formed bybeing connected to the aforesaid pixel electrode. Thus, a high-precisiondisplay reflection type color liquid crystal device can be obtained.

Furthermore, a preferable embodiment of a reflection type color liquidcrystal device, which has a liquid crystal cell, in which a liquidcrystal layer is held between a first substrate provided with areflector electrode and a second substrate provided with a transparentelectrode and a color filter, wherein the liquid crystal cell is placedbetween a pair of polarizing plates, wherein an optical reflector plateis formed outside one of the substrates, and wherein the aforementionedcolor filter comprises filter elements respectively corresponding tosubtractive primaries that are yellow, cyan and magenta color elements,and wherein the lowest transmittance of the color filter, whichcorrespond to each of the color elements, is not more than 10% in avisible region.

Thus, the reflection layer (namely, the reflector electrode) is placedclose to the liquid crystal layer.

Generally, the range of wavelengths from 400 to 770 nm is referred to asthe visible region. Especially, the human visual sensitivity is high inthe range of wavelengths from 450 to 660 nm. Therefore, a bright andclear display can be attained by setting the transmittance of the colorfilter correspondingly to each of all of the color elements in a visiblerange (400 to 770 nm) as above described.

Moreover, a reflection type color liquid crystal device can be obtainedby placing an optical diffusion plate between the second substrate andthe polarizing plate.

Furthermore, regarding the color filter, the lowest transmittancethereof corresponding to each of the color elements in the visibleregion is set at least 20% or more and, more preferably, 30% or more.

On the other hand, a preferable embodiment of the reflection type colorliquid crystal device of the present invention is adapted so that thespectrum representing a transmission characteristic of the aforesaidyellow filter element intersects with the spectrum representing atransmission characteristic of the aforesaid magenta filter element at awavelength being close to 500 nm, wherein the spectrum representing atransmission characteristic of the aforesaid cyan filter elementintersects with the spectrum representing a transmission characteristicof the aforesaid magenta filter element at a wavelength being close to600 nm, and wherein these two points of intersection are present in arange where a transmission is not less than 30%. More preferably, theaforesaid color filter is formed so that the two points of intersectionare present in a range where the transmittance is 35% to 60%.

By using such a color filter, a bright display reflection type colorliquid crystal device can be obtained.

Moreover, a preferable embodiment of the reflection type color liquidcrystal device of the present invention is adapted so that a distancebetween the optical reflector plate and the color filter is set as beinglarger than the pitches of dots formed by the aforesaid electrode. Morepreferably, the distance between the optical reflector plate and thecolor filter is set as being twice to three times each of the dotpitches. Incidentally, it is not desirable that the thickness of theglass substrate becomes larger than 0.7 mm. This is because the doubleimage of the display is conspicuous.

With such a configuration, the color saturation of the displayed colorsis enhanced by the subtractive mixing which utilizes the parallax.

Furthermore, a preferable embodiment of the reflection type color liquidcrystal device of the present invention is adapted so that a pixelelectrode is placed on one of the aforesaid substrates in such a mannerso as to be formed like a matrix, and that a switching element is formedby being connected to the aforesaid pixel electrode. Thus, a clearerdisplay reflection type color liquid crystal device can be obtained.

Additionally, correspondingly to a preferable embodiment of thereflection type color liquid crystal device of the present invention,there is provided a method of driving the aforementioned reflection typecolor liquid crystal device, wherein, when displaying any color with theexception of black, a plurality of dots are turned on or partiallyturned on among 3 dots corresponding to each of the aforesaid yellow,cyan and magenta. In other words, only in the case of displaying black,3 dots are non-illuminated. In the case of displaying 3 colors such asred, green and blue, 2 dots are turned on. In the case of other colors,all of 3 dots are turned on or partly illuminated. Incidentally, theturning-on is defined as an operation of changing the liquid crystaldevice into a bright state. Further, non-illuminating is to put theliquid crystal device into a dark state. Furthermore, an operation ofpartly turning on is to put the liquid crystal device into anintermediate state between the bright and dark states. With such aconfiguration, the reflection type color liquid crystal device canrealize an extremely bright display. Further, the intermediate displaycan be achieved. Thus, the present invention has an advantage in thatfull color display can be attained.

Furthermore, by mounting the reflection type color liquid crystal deviceon the electronic devices, lower power consumption electronic device canbe obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a primary part of the configuration ofa reflection type color liquid crystal device of the present invention;

FIG. 2 is a graph illustrating a spectral characteristic of a colorfilter of the reflection type color liquid crystal device of the presentinvention;

FIG. 3 is a graph illustrating the display colors of the reflection typecolor liquid crystal device of the present invention;

FIG. 4 is a diagram illustrating a primary part of the configuration ofanother reflection type color liquid crystal device of the presentinvention;

FIG. 5 is a diagram illustrating a primary part of the configuration ofstill another reflection type color liquid crystal device of the presentinvention;

FIG. 6 is a diagram illustrating the configuration of yet anotherreflection type color liquid crystal device of the present invention;

FIGS. 7(a)-(b) are a sectional view of a conventional reflection typecolor liquid crystal device using a red-green-blue color filter andutilizing TN mode or STN mode, which is drawn for illustrating theproblems of parallax;

FIGS. 8(a) and 8(b) are a sectional view of a reflection type colorliquid crystal device of the present invention utilizing TN mode or STNmode, which is drawn for illustrating the problems of parallax;

FIG. 9 is a graph illustrating display colors of the conventionalreflection type color liquid crystal device using red-green-blue colorfilters;

FIG. 10 is a graph illustrating display colors of a reflection typecolor liquid crystal device using yellow-cyan-magenta filters; and

FIGS. 11(a)-(c) are a diagram illustrating an example of electronicdevices, each of which is equipped with a reflection type color liquiddevice of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The configuration of a device of the present invention may be consideredto be similar to that of the reflection type liquid crystal devicedisclosed in the aforementioned Japanese Unexamined Patent PublicationNo. 5-241143 Official Gazette. Indeed, these liquid crystal devices aresimilar in respect of the fact that a subtractive-primaries color filteris used.

However, in the case of the device of the present invention, such afilter is applied to liquid crystal modes, such as TN-mode and STN-mode,in which an occurrence of parallax cannot be prevented. Such anapplication of the filter brings new advantageous effects, such aseffects of mitigating the problems of parallax and of enhancing colorpurity by performing a subtractive process, in addition to the effect ofsimply brightening up.

Such new advantageous effects will be described hereinbelow by referringto the drawings. FIGS. 8(a) and 8(b) are sectional views of a reflectiontype color liquid crystal device utilizing TN mode or STN mode. Thisliquid crystal device is composed of an upper polarizing plate 1, anupper glass substrate 2, a liquid crystal layer 3, a lower glasssubstrate 4, a lower polarizing plate 5, an optical reflector plate 6,and a yellow-cyan-magenta primaries color filter 7. In addition, thereare transparent electrodes, an orientation film and an insulating filmbetween the upper and lower glass substrates. However, these composingelements are unnecessary for the description of the problems of parallaxand thus the drawing of these composing elements is omitted.

Meanwhile, the first problem relating to the parallax is colorcancellation. As illustrated in FIG. 8(a), reflection light 31 observedby an observer 32 is a mixture of light rays having propagated throughthe following three paths among color dots: “yellow to cyan”; “magentato cyan”; and “cyan to cyan”. A part of light having passed through thepath “yellow to cyan” among these paths is absorbed and thus is green.Further, light having passed through the path “magenta to cyan” amongthese paths is red. However, different from the case of using thered-green-blue color filter, it does not become completely dark. Thus,although the brightness in the case of displaying white is decreased to⅓ of that in the case of no parallax when using the red-green-blue colorfilter, the brightness in the case of displaying white is decreased to ⅔of that in the case of no parallax when using a yellow-cyan-magentacolor filter.

Further, the second problem of parallax resides in that the colordisplay becomes dark. FIG. 8(b) illustrates a green displaying state.Further, a cross hatched portion in the liquid crystal layer 7 indicatesthat such a portion is in a unilluminated state (or in a dark state). Inthe case of displaying green with the yellow-cyan-magenta filter, yellowand cyan color dots are put into an illuminated state (namely, in abright state), and magenta color dots are brought into the unilluminatedstate (namely, in the dark state). Thus, ⅓ of incident light 30 isabsorbed by magenta dots which are in an off-state. Further, after beingdiffused by the optical reflector plate and mixed, ⅓ of the incidentlight is absorbed by the magenta dots which are in the off-state andthen reaches the observer 32. Therefore, the brightness in the case ofdisplaying green is obtained as follows: “{fraction (4/9)} of thebrightness in the case of displaying white—a part of that to bedecreased owing to the absorption by the cyan and yellow dots”.Consequently, the brightness in the case of displaying green is higherthan that in the case of using the red-green-blue filter.

In addition, a result of the detailed examination of the paths of lightin the case of displaying green reveals that there are the followingfour kinds of paths: “cyan to cyan”, “yellow to yellow”, “cyan toyellow” and “yellow to cyan”. In the case of the latter two of thesepaths, the light passes through both of the yellow and cyan dots, sothat a subtractive color mixture condition occurs.

Namely, owing to the effects of the parallax, both of the additive colormixture due to a planar set of color points and the subtractive colormixture due to a three-dimensional overlap of color points aresimultaneously produced. When using yellow-cyan-magenta (namely,subtractive primaries) color filter, an effect of enhancing the degreeof the color saturation of displayed color is obtained by configuringthe device in such a manner as to cause parallax.

Next, a method of driving the device will be described hereinbelow. FIG.9 is a graph illustrating the displayed colors in the case of aconventional color liquid crystal device using the red-green-bluefilter. Needless to say, in the case of displaying a single color,reference numerals 41, 42 and 43 designate displayed colors in the caseof displaying a single color of red, green and blue, respectively.Needless to say, in the case of displaying a single color, only one dotis illuminated (namely, the bright display thereof is performed) amongthree dots composing one pixel. When the gradation levels of the colordots are determined by performing a halftone correction in this deviceaccording to NTSC primary color signals respectively corresponding tored, green and blue, colors corresponding to the hatched area in thisfigure can be displayed.

On the other hand, FIG. 10 is a diagram illustrating the displayedcolors of the reflection type color liquid crystal device using theyellow-cyan-magenta filter. Reference numerals 44, 45 and 46 designatedisplayed colors in the cases of displaying a single color of yellow,cyan and magenta, respectively. When driving this device similarly as inthe case of the conventional device, colors included in a trianglehaving vertexes 44, 45 and 46 of this figure can be displayed.Incidentally, in the case that there is a parallax, the subtractivecolor mixture results owing to the previously described effects. Rangeof displayed colors is expanded to that indicated by dashed lines inthis figure.

However, it is assumed that only the colors included in the hatched areain the triangle having the vertexes 47, 48 and 49 are displayed in thecase of the device of the present invention. This is because of the factthat two dots or more of three dots of each pixel are illuminated(except in the case of displaying black) in the case of the displayedcolors in this range and thus the bright color display is obtained forthe reason described above with reference to FIG. 8(b). Therefore, whendisplaying, for example, yellow, lighter colors are utilized, which areobtained by turning on all yellow dots but a part of cyan dots and apart of magenta dots, instead of 44 colors which are obtained by turningon a single yellow dot. Thus, about ¾ of the displayable colors are notutilized. Although this may be considered to be inefficient, this hasgreat merits in that a bright and well-balanced display can be obtained.

In the case of the reflection type color liquid crystal device of thepresent invention, first, a high-contrast display is ensured byemploying a liquid crystal display mode using the polarizing plate. Inaddition, this is combined with the subtractive-primaries color filter,so that a bright display is obtained.

Although there are many liquid crystal display modes using polarizingplates, liquid crystal display modes by which bright and black-and-whitedisplays can be realized, for example, TN mode proposed in the JapanesePatent Publication No. 51-013666 Official Gazette, STN mode of the phasedifference plate compensation type proposed in the Japanese PatentPublication No. 3-50249 Official Gazette and a nematic liquid crystalmode proposed in the Japanese Unexamined Patent Publication No. 6-235920Official Gazette which performs a bi-stable switching operation, aresuited for the purpose of the present invention. Among these modes, TNmode is extremely superior in respect that a bright and high-contrastdisplay can be obtained. On the other hand, the degree of the sharpnessof the voltage-transmittance characteristic is low. Moreover, it isnecessary for driving the device of TN mode to place an expensive MIM orTFT element at each dot (or each pixel). Incidentally, STN mode of thephase difference compensation type is more suitable for driving aninexpensive simple matrix.

Further, the liquid crystal mode using only a single polarizing plate,for instance, a single polarizing plate type nematic liquid crystal modeproposed in the Japanese Unexamined Patent Publication Nos. 3-223715 and4-97121 Official Gazettes, and a single polarizing plate type hybridorientation nematic liquid crystal mode announced in a lecture No. 3A19of the 21th liquid crystal panel discussion (1995) can be utilized. Eachof these liquid crystal display modes uses only a single polarizingplate. Thus, a shade in the display can be eliminated by placing thereflector plate in such a manner so as to be close to a liquid crystallayer or a color filter layer. Incidentally, in this case, there is thenecessity for a contrivance to perform mirror finish on the reflectorplate and to provide a diffusing plate on the outer surface of the glasssubstrate to thereby cause a parallax and improve the displayed colors.

Hereinafter, the present invention will be described in detail byreferring to the drawings.

(Embodiment 1)

FIG. 1 is a diagram illustrating a primary part of a reflection typecolor liquid crystal device according to the exemplary embodiment of theinvention.

Reference numeral 1 denotes an upper polarizing plate; 2 an upper glasssubstrate; 3 a liquid crystal layer; 4 a lower glass substrate; 5 alower polarizing plate; and 6 an optical reflector plate. Signal line 9,a pixel electrode 10 and MIM element 11 are formed on the lower glasssubstrate. Incidentally, each of the pairs of elements (1 and 2; 4 and5; and 5 and 6) are drawn as being separated from each other in thisfigure. This is conducted for the reader's clear and ready understandingof the present invention. Actually, such composing elements of each ofthe pairs are glued by using a paste. Further, the upper glass substrate2 and the lower glass substrate 4 are drawn as being spaced far awayfrom each other. This is conducted for the same reason. Actually, thesesubstrates face each other across a gap of several μm to ten-odd μm orso.

Moreover, in this figure, the simplified configuration is described.Namely, 3×3=9 dots are illustrated. Actually, in a liquid crystal panelconsisting of opposed one pair of substrates (2, 4), 480×1920=921600dots are formed. Incidentally, the number of dots of the reflection typecolor liquid crystal device of the present application is not limitedthereto. The present invention can be applied to any reflection typecolor liquid crystal device as long as the device has a plurality ofdots.

Counter electrodes 8 and pixel electrodes 10 are constituted bytransparent electrodes. In the case of this embodiment, the electrodesare constituted by ITO. Signal line 9 is formed by using a metal Ta. MIMelement has a structure in which an insulating film Ta₂O₅ is interposedbetween the metals Ta and Cr. Thickness of the lower glass substrate is0.7 mm. The dot pitch (namely, the pitch between each pair of adjacentpixels) in each of the longitudinal and transverse directions is 0.16mm. Incidentally, TFT may be employed as a switching element.

The thickness of the liquid crystal layer and that of the electrodes arenegligible in comparison with that of the lower glass substrate. Thus,the distance between the optical reflector plate and the color filter is4.4 times the dot pitch.

Liquid crystal layer 3 is made of twisted nematic liquid crystals whosetwist angle is 90°. Thickness of the liquid crystal and that of theliquid crystal layer are set in such a manner that the product of thebirefringence anisotropy of the refractive index (Δn) of the liquidcrystal and the thickness (d) of the liquid crystal layer, namely, theretardation (Δn×d) is equal to 0.48 μm. Moreover, the upper and lowerpolarizing plates are set so that the axis of absorption thereof isnearly parallel with the rubbing axis of an adjacent substrate. This isthe configuration of the brightest TN mode.

Further, the color filter 7 consists of elements respectivelycorresponding to the subtractive primaries, namely, yellow (indicated by“Y” in this figure), cyan (indicated by “C” in this case) and magenta(indicated by “M” in this figure). The color filter is formed outsidethe display area. For example, the color filter is formed in the samearrangement as in the drive area outside the display area (namely, thedrive area) and by the border of the bezel opening area. As a result ofplacing the color filters in this way, the peripheral portion and thedrive portion have the same brightness. The darkness of the driveportion is inconspicuous. Furthermore, even when the liquid crystaldevice is not driven, a display state in which there is no sense ofincongruity to observers can be obtained.

Incidentally, in the case of the reflection type color display device ofthe present invention, no black mask is formed between adjoining colorfilters.

FIG. 2 is a graph showing the spectral characteristic of the colorfilter 7. The horizontal axis represents the wavelength of light (innm); and the vertical axis the transmittance (in %). Reference numeral24 designates the spectrum of the yellow filter element; 25 that of thecyan filter element; and 26 that of the magenta filter element. Thetransmittance characteristic of each color filter element is indicatedby the corresponding spectrum illustrated in FIG. 2. These spectra aremeasured by using a microspectrophotometer. The spectra are measured atthe color-filter-side single substrate. Then, the transmittance of eachof the glass substrates and the transparent electrodes is corrected andadjusted to 100%. In the following cases, the spectral characteristicsof the color filter were measured by this method. This color filter hastransmittance of 10% or more correspondingly to all of the wavelengthsin the range of 450 to 660 nm. Incidentally, FIG. 2 shows that thelowest transmittance is 10% in the wavelength range (generally, in thevisible region) of 400 to 700 nm.

FIG. 3 is a graph illustrating the displayed colors of the reflectiontype color liquid crystal device of “Embodiment 1”. This figure is anX-Y chromaticity diagram. A display range of the reflection type colorliquid crystal device of the present application is indicated by usingthis X-Y chromaticity diagram.

Reference numerals 44, 45 and 46 designate displayed colors respectivelycorresponding to the cases of singly displaying yellow, cyan andmagenta. Needless to say, in this case, only one dot is turned on(namely, the bright display thereof is performed) among three dotscomposing one pixel.

Further, reference numerals 47, 48 and 49 designate the displayed colorsrespectively corresponding to the cases of singly displaying red, greenand blue. The reference numeral 49 denotes a vertex placed outside atriangle having vertexes 44, 45 and 46 and indicates that thesubtractive color mixture occurs concurrently with the additive colormixture and that the color purity is enhanced. Incidentally, themeasurement of the displayed colors is performed by irradiating theliquid crystal panel from all directions by using an integrating spherehaving a diameter M of 120 mm, the inner surface of which is coated withbarium sulfate, and directing the light, which is reflected in thedirection normal to the panel, into a spectrometer.

A change in the displayed color, which is produced when the thickness ofthe lower glass substrate is diversely changed from 0 mm to 1.1 mm inthe reflection type color liquid crystal device of “Embodiment1”described in the foregoing description, will be described in TABLE 1.Incidentally, when the result is that the thickness is 0 mm, thedisplayed color is measured by a cell in which the reflector plate andthe polarizing plates are provided on the cell inner surface.

TABLE 1 Glass Displaying Thickness Displaying Red Green Displaying Blue(mm) x y x y x y 0 0.377 0.337 0.334 0.400 0.290 0.282 0.1 0.386 0.3370.335 0.411 0.282 0.272 0.2 0.387 0.337 0.335 0.413 0.281 0.270 0.30.388 0.337 0.334 0.414 0.280 0.268 0.4 0.390 0.336 0.334 0.416 0.2780.266 0.5 0.392 0.336 0.334 0.448 0.277 0.264 0.55 0.392 0.336 0.3340.419 0.276 0.263 0.7 0.395 0.336 0.334 0.422 0.274 0.261 1.1 0.4010.336 0.335 0.429 0.271 0.255

This table reveals that the color purity of the displayed color isenhanced more and more with an increase in the thickness of glass. Thisis due to the parallax and indicates that the subtractive color mixtureoccurs in the range of the thickness of glass between 0 mm to 0.1 mm.The change in the color purity in the range of the thickness of glassexceeding 0.1 mm seems to be relatively faint.

Therefore, it is considered that if the thickness of glass is of theorder of the magnitude of the dot pitch, the effects of the subtractivecolor mixture due to the parallax occur. More preferably, the thicknessof the glass is 0.5 mm or so, which is about three times the dot pitch,because the color difference (between the cases of respectivelydisplaying a primary color and white) is larger than that of the casethat the thickness of the glass is 0 mm by 20% or more. In view of therelation between the dot pitch and the thickness of the substrate, it isdesirable that the thickness of the substrate is set at a value which isat least about two times, more preferably, about three times the dotpitch.

Next, results of utilizing color filters, which are different in thespectral characteristic from one another, in the reflection the colorliquid crystal device are shown below.

TABLE 2 and TABLE 3 describe the brightness and the displayed colors inthe cases of singly displaying white, red, green and blue. In thesecases, the color filters are utilized, in which the lowest transmittanceis changed from 0% to 30% while the highest transmittance is maintainedat 90% in the spectral characteristic corresponding to each color inFIG. 2. This measurement is also performed by using the aforementionedintegrating sphere. Incidentally, the brightness is normalized bysetting that of the standard white plate at 100%. Moreover, for thepurpose of making comparisons, results of the measurement by using theconventional reflection type color liquid crystal device which employsthe red-green-blue filter, are listed in the lowest rows of thesetables. In these tables, “YCM” indicates the use of theyellow-cyan-magenta color filter; and “RGB” the use of thered-green-blue color filter.

TABLE 2 Lowest Dis- Dis- Dis- Dis- Color Transmit- playing playingplaying playing Filters tance White Y Red Y Green Y Blue Y YCM 0% 11.3%6.4% 9.5% 5.8% YCM 5% 12.0% 6.8% 9.8% 6.2% YCM 10% 12.5% 7.1% 10.0% 6.5%YCM 15% 12.9% 7.3% 10.1% 6.8% YCM 20% 13.3% 7.5% 10.2% 7.0% YCM 25%13.6% 7.7% 10.3% 7.2% YCM 30% 13.9% 7.8% 10.4% 7.4% RGB 50% 13.4% 3.5%4.7% 3.3%

TABLE 3 Color Lowest Displaying White Displaying Red Displaying GreenDisplaying Blue Filter Transmittance X Y X Y X Y X Y YCM  0% 0.331 0.3380.402 0.335 0.334 0.431 0.268 0.254 YCM  5% 0.331 0.338 0.339 0.3360.334 0.427 0.271 0.258 YCM 10% 0.331 0.338 0.395 0.336 0.334 0.4220.274 0.261 YCM 15% 0.331 0.338 0.392 0.337 0.334 0.418 0.277 0.265 YCM20% 0.331 0.338 0.388 0.337 0.334 0.413 0.280 0.268 YCM 25% 0.331 0.3380.385 0.338 0.334 0.409 0.283 0.272 YCM 30% 0.331 0.338 0.381 0.3380.334 0.404 0.286 0.275 RCB 50% 0.332 0.339 0.384 0.384 0.335 0.4090.284 0.272

As is seen from these tables, it is found that the larger the lowesttransmittance of the color filter becomes, the brighter display isobtained and that however, the larger the lowest transmittance of thecolor filter becomes, the lighter the displayed color becomes.Incidentally, the change in the displayed color is very faint, so thatit is advantageous to obtain the brighter display by raising the lowesttransmittance of the color filter. Therefore, the lowest transmittanceof the color filter should be 10% or more, more preferably, 20% or more.

As described above, when raising the lowest transmittance, the displayedcolor becomes lighter. Thus, it is desirable that the characteristic ofeach color filter is set so that the lowest transmittance is within therange between 15% and 25%. As a result of setting the lowesttransmittance of the color filter corresponding to each color element insuch a manner as to be within this range, the reflection type colorliquid crystal device, which can realize the bright and clear display,is obtained.

Such results are compared with those of the measurement by using theconventional reflection type color liquid crystal device employing thered-green-blue filter. As is seen from TABLE 3, the yellow, cyan andmagenta filter elements, by which the obtained displayed colors arenearly the same as those obtained by using the conventional reflectiontype color liquid crystal device employing the red-green-blue filterwhose lowest transmittance is 50%, have the lowest transmittance of 25%.Comparisons between the brightness of the displays obtained by thesedevices in TABLE 2 show that when displaying white, the brightnessobtained by the device according to this embodiment is almost the sameas that obtained by the conventional device, and that when displayingred, green and blue, the brightness obtained by using the yellow, cyanand magenta filter elements is higher by about 2.2 times that obtainedby the conventional device. This is due to the effect of turning on twodots among the three dots in each pixel in the case of the device ofthis embodiment.

(Embodiment 2)

A similar reflection type color liquid crystal device can be configuredby utilizing STN mode.

FIG. 4 is a diagram illustrating the primary part of the configurationof the reflection type color liquid crystal device according to theexemplary embodiment of the invention.

Reference numeral 1 denotes an upper polarizing plate; 14 a phasedifference film; 2 an upper glass substrate; 3 a liquid crystal layer; 4a lower glass substrate; 5 a lower polarizing plate; and 6 an opticalreflector plate. Scanning electrodes 8 and a color filter 7 are providedon the upper glass substrate 2. Signal electrodes 15 are provided on thelower glass substrate.

Scanning electrodes 8 and signal electrodes 15 are formed by usingtransparent ITO. Thickness of the lower glass substrate is 0.7 mm. Thedot pitch (namely, the pitch between each pair of adjacent pixels) ineach of the longitudinal and transverse directions is 0.16 mm. Thedistance between the optical reflector plate and the color filter is 4.4times the dot pitch.

Color filter 7 is composed of elements respectively corresponding to thesubtractive primaries, namely, yellow (indicated by “Y” in this figure),cyan (indicated by “C” in this case) and magenta (indicated by “M” inthis figure). Incidentally, to obtain a bright display, no black mask isformed between adjoining color filters.

Liquid crystal layer 3 is made of twisted nematic liquid crystals inwhich a twist angle of the liquid crystal molecule is 240°. Phasedifference film 14 is constituted by a uniaxial oriented film made ofpolycarbonate. This is of STN mode of the phase difference compensationtype proposed by the Japanese Patent Publication No. 3-50249 OfficialGazette. Further, the display of black on a white background or that ofwhite on a black background can be obtained by suitably selecting theretardation between the liquid crystal layer and the phase differencefilm and the relation between the axes thereof. In the case of thisembodiment, when determining the conditions for compensating color stainoccurring on STN type liquid crystal panel, the display of black wasregarded as more important from the viewpoint that even if the colorstain was slightly left in the display of white, the color stain wascompensated by the color filter.

This reflection type color liquid crystal device (hereunder referred tosimply as a liquid crystal panel) was driven by a multi-line drivingmethod, by which a plurality of lines are simultaneously selected. Thus,a frame response suppressing effect was produced as disclosed in theJapanese Unexamined Patent Publication No. 6-348230 Official Gazette.Consequently, a high contrast display was obtained. Incidentally, in thecase of using the driving method, by which a plurality of lines weresimultaneously selected, a signal applied to the scanning electrode wasestablished on the basis of orthogonal functions. At that time, thepreferable number of the scanning electrodes is 4. Moreover, in the caseof this driving method, a scanning signal to be applied to the scanningelectrodes has a plurality of selection time periods. Preferably, thenumber of such selection time periods is 4.

Display characteristics of this embodiment is nearly equivalent to thoseof “Embodiment 1”. However, the brightness of the display obtained by“Embodiment 2” is higher by a degree corresponding to the absence of themetallic signal line 9 illustrated in FIG. 1. Further, the displayedcolor in the case of this embodiment is a little lighter by a degreecorresponding to the fact that the contrast obtained in this embodimentis lower than that obtained by “Embodiment 1”.

(Embodiment 3)

Next, an example of a reflection type color liquid crystal deviceutilizing the liquid crystal display mode of the single polarizing platetype, in which polarizing plates are placed only at thelight-impinging-substrate-side, will be described hereinbelow.

FIG. 5 is a diagram illustrating a primary part of the configuration ofthe reflection type color liquid device according to the presentinvention.

Reference numeral 1 designates an upper polarizing plate; 17 a lightdiffusing plate; 14 a phase difference film; 2 an upper glass substrate;3 a liquid crystal layer; and 4 a lower glass substrate.

Scanning electrodes 8 and the color filter 7 are formed on the upperglass substrate 2. Further, the signal electrodes 15 also acting asreflector plates are formed on the lower glass substrate 4. The scanningelectrodes 8 are formed by using transparent ITO. Further, the signalelectrodes (namely, the reflectors) 16 also serving as reflector platesare formed by using metallic aluminum. Incidentally, the reflectors 16having mirror reflection plates are formed in this manner.

Preferably, the light diffusing plate 17 has a filler structure but doesnot cause a phase difference. For example, AGSI manufactured by NittoDenko Corporation is preferable as the light diffusion plate 17.Further, in this embodiment, the light diffusion plate is providedbetween the polarizing plate and the upper glass substrate. Thediffusion plate, however, may be provided on the polarizing plate.

Color filter 7 is composed of elements respectively corresponding to thesubtractive primaries, namely, yellow (indicated by “Y” in this figure),cyan (indicated by “C” in this case) and magenta (indicated by “M” inthis figure). Incidentally, to obtain bright display, no black mask isformed between adjoining color filters.

Liquid crystal layer 3 is made of twisted nematic liquid crystals inwhich the liquid crystal molecules are oriented in a twisted arrangementat a twist angle of 240°. Phase difference film 14 is constituted by auniaxial oriented film made of polycarbonate. Basically, this is of theliquid crystal display mode of the phase difference compensation typeproposed by the Japanese Unexamined Patent Publication No. 4-97121Official Gazette. Further, the display of black on a white background orthat of white on a black background can be obtained by suitablyselecting the retardation between the liquid crystal layer and the phasedifference film and the relation between the axes thereof.

Incidentally, the number of the phase difference plates is not limitedto 1. To cancel the coloring peculiar to STN type liquid crystal, aplurality of phase difference plates may be provided in the device.

In the case of the device of this type, the reflector plate was providedclose to the liquid crystal layer and the color filter layer. Thus, ashadow of the display (namely, a double image) can be eliminated.Moreover, the light necessarily passes through the same color filtertwice, so that a bright low-color-purity color filter can be utilized.Furthermore, the light diffusion plate placed in such a manner as to bespaced from the color filter causes subtractive color mixture due tomultiple reflection in a part of the device. Clearer and brighter colorscan be displayed.

Incidentally, in the case of this embodiment, the driving methoddescribed in the foregoing description of “Embodiment 2”, by which aplurality of lines are selected simultaneously, can be employed.

(Embodiment 4)

This embodiment is a modification of the configuration of “Embodiment3”. Namely, as illustrated in FIG. 6, the pixel electrodes (namely, thereflectors) 10 and switching elements 11 are formed on the substrate 4.

Pixel electrodes are formed in a matrix. Further, this pixel electrodeis made of a metal having the reflection characteristics. For instance,aluminum, chromium and nickel may be used.

Further, as shown in FIG. 6, MIM elements are used as switchingelements. Incidentally, TFT is a semiconductor substrate formed byutilizing semiconductor techniques. Reflectors are placed in such amanner as to cover the switching elements. With such a configuration,the reflectors can be formed with high precision. Especially, thesurface coming in contact with the liquid crystal layer provided on thesubstrate is formed almost only by the reflectors. Thus, this embodimenthas many reflection surfaces, so that the reflection type liquid crystaldevice, which is superior in respect of the reflecting characteristicscan be obtained.

Incidentally, the liquid crystal layer 3 is established so that theliquid crystal molecules are oriented in a twisted arrangement at atwist angle of 90°. However, the twist angle of the liquid crystal isnot limited to 90° and is sometimes set at an angle within a range of60° to 80°. This is because the twist angle of the liquid crystalmolecules is set in such a manner that light having been incident on theliquid crystal layer is changed into almost linearly polarized light onthe surface of the reflector (namely, the pixel electrode). To that end,it is necessary to suitably set the product of the birefringenceanisotropy of the refractive index (Δn) of the liquid crystal and thethickness (d) of the liquid crystal layer, and the twist angle.

Moreover, the color filter is formed by using the yellow, cyan andmagenta elements, similarly as in the aforementioned embodiment.Furthermore, no black mask is provided so as to ensure the brightness ofthe liquid crystal device.

Incidentally, in the case of this embodiment, the light diffusion plate17 is provided between the substrate 2 and the polarizing plate 1, withthe intention of realizing the bright and clear display. Preferably, thelight diffusion plate 17 has a filler structure but does not cause aphase difference. For example, AGSI manufactured by Nitto DenkoCorporation is suitable for the light diffusion plate 17. Further, inthis embodiment, the light diffusion plate is provided between thepolarizing plate and the upper glass substrate. The light diffusionplate, however, may be provided on the polarizing plate.

Furthermore, in the case of this embodiment, the reflector plate isprovided close to the liquid crystal layer and the color filter layer.Thus, a shadow of the display (namely, a double image) can beeliminated. Moreover, the light necessarily passes through the samecolor filter twice, so that a bright low-color-purity color filter canbe utilized.

Namely, in the case of this device of the present application, asdescribed in the foregoing tables, it is preferable that the lowesttransmittance of all of the filter elements of the color filterconsisting of the yellow, magenta and cyan filter elements is 10% ormore, more preferably, 20% or more. Further, if the lowest transmittanceis 30% or more, a clear display can be attained.

In the case of this embodiment, the light necessarily passes through thesame color filter twice, differently from the aforesaid “Embodiment 1”.Thus, a display having the color purity, the level of which is at leastequal to that obtained in the device using the red-green-blue colorfilter, can be obtained by using the color filter whose lowesttransmittance is 30% or more. Moreover, the reflection type color liquidcrystal device of the present application using the color filtercomposed of the yellow, magenta and cyan elements can obtain a displaythe brightness of which is far higher than that of a display obtained bythe device using the red-green-blue color filter.

Further, regarding this embodiment, the characteristic of the colorfilter is shown in FIG. 2 by way of example. As illustrated in thisgraph, a curve representing the spectrum 24 of the yellow filter elementintersects with another curve representing the spectrum 26 of themagenta filter element at the wavelength in the vicinity of 500 nm. Thispoint of intersection of the two spectra corresponds to thetransmittance of nearly 50%. Further, at a wavelength in the proximityof 600 nm, a curve representing the spectrum 25 of the cyan filterelement intersects with a curve representing the spectrum 26 of themagenta filter element. This point of intersection of the two spectracorresponds to the transmittance of almost 40%.

It is preferable that these two points of intersection are present in arange in which the transmittance is at least 30%. In the case of thecolor filter by which these two points of intersection are present in arange where the transmittance is lower than 25%, the decoloring of thelight having the wavelengths corresponding to the points of intersectionoccurs. Thus, no clear displays are obtained. Therefore, the colorfilter should be designed so that the two points of intersection arepresent, namely, the curves representing the spectra intersect with eachother in a range where the transmittance is 30% or more. Morepreferably, the device employs the color filter designed so that the twopoints of intersection are present, namely, the curves representing thespectra intersect with each other in the neighborhood of thetransmittance of 35% to 60%. Thereby, a more clear display can beobtained.

Incidentally, the wavelengths corresponding to the two points ofintersection are indicated by way of example in the embodiments of thepresent application and are thus not limited to 500 and 600 nm,respectively.

Additionally, in the case of this embodiment, the color filter is placedon the liquid-crystal-layer-side surface of the substrate 2. However,the placement of the color filter is not limited thereto. Color filtermay be placed on the polarizing-plate-side surface of the substrate.With such a configuration, the parallax due to the thickness of thesubstrate can be utilized and a clear display can be obtained, similarlyas in the case of the aforementioned “Embodiment 1”.

Incidentally, an isotropic layer having optical isotropy can be placedon the inner or outer surface of the substrate.

(Embodiment 5)

In the case of driving the reflection type color liquid crystal layersdescribed as “Embodiment 1” to “Embodiment 4”, when displaying any colorwith the exception of black, a plurality of dots are turned on or partlyilluminated among the three dots corresponding to each of the yellow,cyan and magenta.

More precisely speaking, only when displaying black, all of the threedots are non-illuminated, while all or a part of the three dots areturned on when displaying the other colors. In this case, the expression“a part of the three dots are turned on” indicates that the liquidcrystal device is put into an intermediate state between the brightstate and the dark state. Preferably, the brightness of a display insuch an intermediate state is not less than half of the brightness ofthe brightest dot.

This will be described hereunder more specifically. Reflection typecolor liquid crystal device of “Embodiment 1” has the capability ofdisplaying the colors in the range having vertexes 44, 48, 45, 49, 46,47 and 44 of FIG. 3. In the case of performing the multi-color displaywithout aiming at the reproduction of natural colors, all of the colorsincluded in such a range may be utilized.

However, the colors corresponding to the vertexes 44, 45 and 46 areclear, but are dark because only one dot of the three dots composingeach single pixel is turned on (namely, the bright display is performedon only one dot thereof). Thus, these colors are discarded, and thecolors included within a triangular range having vertexes 47, 48 and 49of this figure are displayed. In the case of these displayed colors inthis range, two dots or more of the three dots corresponding to eachpixel are always turned on (except in the case of displaying black).Thus, the effects of the parallax are alleviated. Consequently, the verybright display of such colors are obtained.

In the case of such a method, almost ¾ of the displayable colors are notutilized. Thus, apparently, such a method is ineffective. However, sucha method is very convenient to obtain a bright display and awell-balanced color display. Especially, in the case of performing thedisplay of colors, which are very close to natural colors, on the basisof NTSC color TV signals, this method is the most suitable one.

(Embodiment 6)

FIGS. 11(a)-(c) show external views of electronic devices respectivelyusing the reflection type liquid crystal panels of the presentinvention.

FIG. 11(a) is a perspective view of a portable telephone. Referencenumeral 1000 designates the main body of the portable telephone; and1001 a liquid crystal display portion using the reflection type liquidcrystal panel of the present invention.

FIG. 11(b) is a diagram or perspective view illustrating an wrist watchtype electronic device. Reference numeral 1100 denotes the main body ofthe watch; and 1101 a liquid crystal display portion using thereflection type liquid crystal panel of the present invention.

This liquid crystal panel has high-precision pixels in comparison withthe display portions of conventional wrist watches. Thus, an imagedisplayed on the screen of TV set can be displayed thereon.Consequently, a wrist watch type TV can be realized.

FIG. 11(c) is a diagram illustrating the portable information processingunit such as a word processor or a personal computer. Reference numeral1200 designates an information processing unit; 1202 an input portionsuch as a keyboard; 1206 a display portion using the reflection typeliquid crystal panel; and 1204 the main unit of the informationprocessing unit.

Each of these electronic devices is battery-operated. Thus, when usingthe reflection type liquid crystal panel which does not have alight-source lamp, the life of the battery can be increased. Further, asin the case of the device of the present invention, the peripheralcircuits can be incorporated into the panel substrate. Consequently, thenumber of parts can be considerably decreased. Moreover, the weight andsize of the device can be further reduced.

What is claimed is:
 1. A reflection type color liquid crystal deviceincluding a liquid crystal cell, the reflection type color liquidcrystal device comprising: a first substrate provided with a firsttransparent electrode, a second substrate provided with a secondtransparent electrode and a color filter, a liquid crystal layerdisposed between the first substrate and the second substrate, a pair ofpolarizing plates between which said liquid crystal cell is placed, andan optical reflector plate formed outside one of said first substrateand said second substrate, wherein said color filter comprises a yellowfilter element, a cyan filter element, and a magenta filter element, andwherein each of the yellow filter element, the cyan filter element andthe magenta filter element transmits more than 15% of all wavelengthlight in the region between 400 nm and 770 nm.
 2. The reflection typecolor display device according to claim 1, wherein a lowesttransmittance of each of the yellow filter element, the cyan filterelement and the magenta filter element is set at a value greater than20% but no more than 25% in the visible region.
 3. The reflection typecolor liquid crystal device according to claim 1, wherein a spectrumrepresenting a transmission characteristic of said yellow filter elementintersects with a spectrum representing a transmission characteristic ofsaid magenta filter element at a first point of intersection at awavelength is approximately 500 nm, wherein a spectrum representing atransmission characteristic of said cyan filter element intersects withsaid spectrum representing a transmission characteristic of said magentafilter element at a second point of intersection at a wavelength isapproximately 600 nm, and wherein the first point of intersection andthe second point of intersection are present where the transmittance ismore than 30%.
 4. The reflection type color liquid crystal deviceaccording to claim 3, wherein the first point of intersection and thesecond point of intersection are present where a transmittance is 35% to60%.
 5. The reflection type color liquid crystal device according toclaim 1, wherein a distance between the optical reflector plate and thecolor filter is larger than dot pitches.
 6. The reflection type colorliquid crystal device according to claim 5, wherein the distance betweenthe optical reflector plate and the color filter is twice to three timeseach of the dot pitches.
 7. The reflection type color liquid crystaldevice according to claim 1, further comprising pixel electrodes placedon one of said first substrate and said second substrate in a matrix,and a switching element connected to said pixel electrodes.
 8. A colorliquid crystal device including a liquid crystal cell, the color liquidcrystal device comprising: a first substrate provided with a reflector,a second substrate, a liquid crystal layer disposed between the firstsubstrate and the second substrate, and a color filter positionedbetween the first substrate and the second substrate, wherein said colorfilter comprises a yellow filter element, a cyan filter element, and amagenta filter element, and wherein each of the yellow filter element,the cyan filter element and the magenta filter element transmits morethan 15% of all wavelength light in the region between 400 nm and 770nm.
 9. The color liquid crystal device according to claim 8, wherein anoptical diffusion plate is placed between the second substrate and apolarizing plate.
 10. The color liquid crystal device according to claim8, wherein a lowest transmittance is 20% or more in the visible region.11. The color liquid crystal device according to claim 10, wherein thelowest transmittance is 30% or more in the visible region.
 12. The colorliquid crystal device according to claim 8, wherein a spectrumrepresenting a transmission characteristic of said yellow filter elementintersects with a spectrum representing a transmission characteristic ofsaid magenta filter element at a first point of intersection at awavelength is approximately 500 nm, wherein a spectrum representing atransmission characteristic of said cyan filter element intersect withsaid spectrum representing a transmission characteristic of said magentafilter element at a second point of intersection at a wavelength isapproximately 600 nm, and wherein the first point of intersection andthe second point of intersection are present where a transmittance ismore than 30%.
 13. The color liquid crystal device according to claim12, wherein the first point of intersection and the second point ofintersection are present where the transmittance is 35% to 60%.
 14. Thecolor liquid crystal device according to claim 8, further comprising: anoptical reflector plate formed outside one of the first and secondsubstrates, wherein a distance between the optical reflector plate andthe color filter is larger than dot pitches.
 15. The color liquidcrystal device according to claim 14, wherein the distance between theoptical reflector plate and the color filter is twice to three timeseach of the dot pitches.
 16. The color liquid crystal device accordingto claim 8, further comprising pixel electrodes placed on one of saidfirst substrate and said second substrate in a matrix, and switchingelements connected to said pixel electrodes.
 17. An electronic devicecomprising said reflection type color liquid crystal device according toclaim
 1. 18. An electronic device comprising said color liquid crystaldevice according to claim 8.